Liberia's Defence Minister, Brownie Samukai told the BBC's Network Africa programme that to his knowledge expenditure this year alone included sums of $11m and $35m "for training, equipment, facilities, buildings and construction - a combination of these types of expenditure."

The researchers say that although the number of armed conflicts is falling in Africa there is no room for complacency, with little hope of a swift settlement in either Sudan or Somalia.

And some experts argue that Africa actually needs to increase its arms spending.

Helmoed-Romer Heitman - the Africa correspondent for Jane's Defence - told the BBC "in a lot of countries the primary problem is that the national security forces are too small, too ill-equipped and too ill-trained to actually provide any sort of security".

He cites the example of Cameroon which has some 12,500 troops to cover around 400,000 sq kms with no transport or reconaissance aircraft.

"Without helicopters for tactical movement", says Mr Heitman, "it's physically impossible for them to deploy to counter banditry or insurgency".

He concludes that most African countries need to spend more on military equipment - but primarily on transport such as helicopters to allow them to mobilise to deploy against the "bad guys".